The production of on-purpose butadiene by oxidative dehydrogenation process requires a large amount of diluents. The on-purpose butadiene is a process that can convert n-butenes to butadiene. Conventionally, steam is used as a diluent to control the exothermic temperature rise in the reactor and provide dilution. This prevents undesired side reactions. The steam may be used to maintain catalyst activity. Typically, the molar ratio of steam to butene in the reactor ranges from 5 to 20. Also, water may be generated in addition to steam in the process of production of butadiene by oxidative dehydrogenation. The hydrogen atoms removed in the reaction are converted to water by addition of air or oxygen enriched stream.
The combined steam fed to the process and the steam generated during the process need to be removed from the product for recovery and purification of the butadiene product. Generally, the steam is removed as water by condensation. But, any heavy hydrocarbons and oxygenates in the reactor effluent will also be condensed along with steam and the water that leaves the reactor includes heavy hydrocarbons and oxygenates.
The water balance for the process favors the recycling of the condensed water to generate steam required for the reactor. Conventionally, an evaporator is used to generate steam from the condensed water. The hydrocarbons that are not evaporated for a hydrocarbon layer on top of the evaporated water and eventually grow with time. This results in fouling of the heat exchange surface in the boiler, high temperature, and potential slugs of the vaporized hydrocarbon.
Therefore, there is need for an improved process for energy efficiency and heat recovery in the oxidative dehydrogenation process. In addition, there is a need for an improved process for steam generation from the water generated in oxidative dehydrogenation reaction that can overcome the above mentioned problems and undesired side reactions.